In the manufacture of tissue products, such as facial tissues, the developments over the years have led to ever-increasing production speeds, and at the current time the production speeds of the papermaking machinery is upwards of 5000 feet per minute, generally in the range of 3000 to 6500 feet per minute. The aqueous slurry of pulp is deposited on the forming fabric (fourdrinier wire) at the head box, and the water from the slurry is drained through the wire at the wet end of the papermaking machine. From the fourdrinier wire, the dewatered pulp is transferred to a felt which expresses further water from the pulp before it is transferred to the Yankee dryer. As the paper is stripped from the Yankee dryer, it is creped by the doctor blade and is wound onto rolls for subsequent converting into facial tissue, toweling, or the like.
Softness has been a desirable characteristic of the tissue products, and there has been a continuing effort to provide enhanced softness without sacrificing strength. Efforts to improve softness have included embossing during the subsequent conversion of the webs into tissue, toweling or the like. The embossing provides a tactile characteristic to the product which combines with a visual cloth-like look to enhance the impression of softness upon the consuming public.
Previous efforts to provide a pattern effect have been directed to the dry end of the process inasmuch as it was believed that the high-speed production techniques used in tissue-making required the maximum uniformity in the sheet formed on the forming wire with a minimum of density variation or basis weight variation throughout the area of the sheet. Pinholing in the sheet resulting from non-uniform disposition of pulp on the wire was believed to be particularly disadvantageous since the appearance of pinholes normally was accompanied by a difficulty in stripping the tissue off the forming fabric and creping the paper as it comes from the Yankee dryer.
The conventional teaching is to form a lightweight sheet of tissue by using a forming fabric with a fine mesh so as to assure uniform basis weight throughout the sheet, which also produces a smooth, non-texturized sheet which is readily released from the forming fabric onto the press or dryer felt.